In an ideal situation, a transmitter may transmit information over a channel or medium and the transmitted information may be received without alteration and processed by a receiver. However, a transmission medium or channel may be constantly subjected to impairments such as noise and interference. Consequently, when a transmitter transmits information, a receiver may not receive the information in an identical manner in which it was transmitted. This may be due to impairments in a channel that may typically introduce errors in the transmitted information. A transmitter may code the data in such a manner that error introduced during transmission may be detected and/or corrected during reception.
In telecommunication, forward error correction (FEC) is a system of error control for data transmission, whereby the sender adds redundant data to its messages, which allows the receiver to detect and correct errors without the need to ask the sender for additional data. The advantage of forward error correction is that retransmission of data can often be avoided, at the cost of higher bandwidth requirements on average, and is therefore applied in situations where retransmissions are relatively costly or impossible.
Today's Internet Protocol Television (IPTV) applications require movement of large data files and content that may include gigabytes of data across IP networks. These IP networks may include carrier access networks such as digital subscriber line (DSL) and/or cable networks, the public Internet or local wired and wireless LANs in customer premises. The IP networks may be capable to transport data packets, but by nature are best effort networks. In other words, if unexpected network conditions such as congestion is encountered, data packets may be dropped based on certain policies. The use of transport control protocol (TCP), an upper layer protocol above IP, may enable requesting retransmission of the lost packets from the origin, and therefore guaranteeing reliability at the expense of possible latency. The TCP/IP may be useful for non-time critical data, for example, unicast data between a server and a client. However, in many cases such as broadcast video, the same content may reach thousands of customers, and multicast IP network delivery may be the best available choice and in such cases, TCP/IP may be unsuitable.
The real-time transport protocol (RTP) may be enabled to provide end-to-end delivery services for data with real-time characteristics such as interactive audio and video applications. Applications typically run RTP above the user datagram protocol (UDP) to make use of its multiplexing and checksum services. The RTP protocol may support data transfer to multiple destinations using multicast distribution if provided by the underlying network.
The use of protocols based on UDP may be capable of multicast operation, but may be unable to request retransmissions. In such cases, a forward error correction code (FEC) may be utilized to recover lost packets in transit over UDP. The Reed-Solomon error correction is an error-correcting code that works by oversampling a polynomial constructed from the data. The polynomial may be evaluated at several points, and these values are sent or recorded. By sampling the polynomial more often than is necessary, the polynomial may be over-determined. As long as many of the points are received correctly, the receiver can recover the original polynomial even in the presence of a few bad points. The Reed-Solomon error correction may require multiplicative operation and dedicated hardware coprocessors, as multiplication and division are expensive for general purpose CPUs in terms of clock cycles.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.